This invention relates to a control device of a refrigerating apparatus, and more particularly, to a control device ofa refrigerating apparatus for a vending machine which has a plurality of storage chambers.
To meet the variety of consumer tastes, vending machines must store and dispense various types of merchandise, each of which may need to be stored at a different temperature. FIG. 1 illustrates such a vending machine 1, the machine being divided internally into a plurality of storage chambers 1a,1b and 1c for storing different types of merchandise, and includes a refrigerating apparatus and heating devices 5a, 5b and 5c for controlling the temperature in each of the chambers.
The main refrigeration components, such as compressor 9 and condenser 7, are disposed in a chamber 2 formed below the storage chambers and are ventilated by a blower or fan 8. Some of the refrigeration components such as evaporators 3a,3b, and 3c, are disposed in storage chambers 1a, 1b, and 1c, respectively, to refrigerate each chamber. These refrigerating components are coupled in series to form a closed refrigerant circuit as shown in FIGS. 2a and 2b. Referring again to FIG. 1, air is circulated in each of the chambers 1a,1b and 1c by a blowers or fans 4a,4b and 4c. The refrigerating temperature in each storage chamber is controlled by thermostats 6a,6b and 6c, and the heating temperature is controlled by thermostats 6d,6e and 6f.
As shown in FIG. 2a, evaporators 3a,3b and 3c are connected in series with electromagnetic valves 10a,10b and 10c and the resulting evaporator-electromagnetic valve combinations are connected in parallel. These parallel combinations are connected in series with compressor 9, condenser 7, capillary tube 12 and accumulator 11. Electromagnetic valves 10 control the refrigerant flow and capillary tube 12 functions as an expansion valve or decompression device. Alternatively, as shown in FIG. 2b, the parallel combination may include capillary tubes 12a,12b, and 12c instead of capillary tube 12 shown in FIG. 2a.
In the above refrigerating circuit, the elements combined in parallel are connected to the circuit in series through distributor 13, shown in more detail in FIG. 3.
One problem associated with the use of a device such as distributor 13 is that the flow of fluid may not be uniform through each of the branches in the parallel network. As a result, the refrigerating efficiency in evaporators 3a,3b and 3c may not be properly balanced. This unequal flow of refrigerant may result in the temperature of one of the chambers remaining above the predetermined level. FIG. 4 illustrates such a result, where the temperature in chamber 1c remains above a predetermined level. An unequal flow of refrigerant causes extended operation of the refrigerating apparatus which increases the operating cost of the vending machine and necessitates a compressor with a large capacity.